Ghost CMS Member Signin Email Enumeration Vulnerability

Executive Summary

This vulnerability affects the Ghost content management system versions from 5.18.0 up to 6.21.1. It involves a discrepancy in the responses from the members signin endpoints, which allows an unauthenticated attacker to determine whether a specific email address is registered as a member on a Ghost site.

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Compliance Impact

This vulnerability allows an unauthenticated attacker to determine whether a specific email address is registered on a Ghost site by exploiting response discrepancies from the members sign-in endpoints.

Such information disclosure could potentially impact compliance with privacy regulations like GDPR and HIPAA, which require protection of personally identifiable information (PII) such as email addresses.

By exposing membership status linked to email addresses without authentication, the vulnerability may lead to unauthorized data exposure, which is a concern under these regulations.

Mitigating this risk by updating to the patched version 6.21.1 is important to maintain compliance and protect user data.

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Impact Analysis

The vulnerability can impact you by allowing attackers to verify if an email address is registered on your Ghost site without authentication. This could lead to targeted phishing attacks or other social engineering attempts against your users.

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Mitigation Strategies

To mitigate this vulnerability, you should upgrade Ghost to version 6.21.1 or later, where the issue has been fixed.

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Detection Guidance

This vulnerability involves discrepancies in responses from the members sign-in endpoints of Ghost versions 5.18.0 to 6.21.0 that allow an unauthenticated attacker to verify if an email address is registered.

To detect this vulnerability on your system, you can test the members sign-in endpoints by sending sign-in requests with different email addresses and observing if the responses differ in a way that reveals registration status.

For example, you can use curl commands to send POST requests to the sign-in endpoint with various email addresses and compare the responses.

• curl -X POST https://your-ghost-site.com/members/api/authentication/token -d '{"email":"[email protected]","password":"any"}' -H 'Content-Type: application/json'
• curl -X POST https://your-ghost-site.com/members/api/authentication/token -d '{"email":"[email protected]","password":"any"}' -H 'Content-Type: application/json'

If the responses differ in a way that indicates whether the email is registered or not, your system is vulnerable.

To mitigate this vulnerability, update Ghost to version 6.21.1 or later.

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